Electron tube device



Oct. 21, 1941. R ER 2,260,274

ELECTRON TUBE DEVICE Filed March 4, 1939 [n vemor:

Felix Herriyer flllarney.

Patented Oct. 21, 1941 UNITED STATES PATENT OFFICE ELECTRON TUBE DEVICE Application March 4, 1939, Serial No. 259,715 In Germany March 5, 1938 5 Claims.

This invention relates to electron tube devices, and more particularly to that type of tubes which is adapted to generate and amplify ultra high frequency oscillations.

It is taught by investigations carried out with electron discharge devices employed for generating or amplifying ultra short oscillations with wavelengths less than 3 meters that the intrinsic capacity of the electrodes of such tubes and also the inductances of the different conductors leading to these electrodes assume such high values that it is practically impossible to amplify such ultra short waves. A further difliculty consists in the fact that the aforementioned high capacitance and inductance values easily cause the tube to build up to self-excitation on account of reactive effects of the various impedances thereof.

It has been proposed in order'to overcome this harmful tendency of self-excitation to provide this type of tubes with a neutralization system, such as a cold electrode assembly as described in my co-pending application Serial No. 229,245, filed September 10, 1938, or suitably interconnected condensers and inductance coils, but this facility has not been able to involve the desired effect, since it is impossible to secure perfect neutralization during operation although the various impedances have been mutually balanced with the best of accuracy before the tube was finished. The reason for this impossibility is that the getter material deposited on the inner surface of the tube envelope during the course of the manufacturing process becomes charged during operation. This metallic getter material which becomes charged to an indeterminable potential exerting an uncontrollable influence upon the above mentioned system or systems subjects the initially proper relationship between the impedances of the tube to considerable variations. This deleterious effect is in the first instance due to the non-symmetric distribution of the getter material on a comparatively small portion of the vacuum tube envelope.

The present invention has for its object to provide means in order to eliminate the above mentioned disadvantages. This is realized according to the main feature of my invention by so surrounding the actual electrode system and the neutralization system mounted in the vacuum envelope of an electron tube that the neutralization action involved therein is rendered immune against any influence from the getter material deposited on the inner surface of the envelope. In one specific aspect of the invention a cagetype of shielding which is maintained at ground potential is located adjacent the inner wall of the envelope so as to encircle the electrode and neutralization systems. This shielding may according to a further feature of this invention be formed directly on the inner wall of the envelope as a coating of colloidal graphite. According to still a further feature, the envelope itself may be of metal which is maintained at the earths potential.

The manner in which my invention is put into effect will be readily understood from the following description taken in conjunction with the accompanying drawing, in which Fig. 1 shows a diagrammatic longitudinal cross section through a vacuum tube to which the invention is applied, while Fig. 2 is a diagrammatic cross sectional view through the embodiment shown in Fig. 1.

In the drawing, reference numeral l indicates the envelope of a vacuum tube. A first electrode assembly comprising a grid 2 and a cathode 4 and a second electrode assembly having a grid 3 and a cathode 5 are arranged in this envelope. The cathodes 4 and '5 are of the flat type. Only :1 one major surface of each cathode is coated with a substance which is capable of emitting electrons so it will be obvious that merely the so coated surface forms part of an effective electrode system, while the not coated rear surface is used as a member of a neutralization system. The reference numerals 6 and 1 denote two anodes common to both the first and the second of the above mentioned electrode assemblies. The two cathodes 4 and 5 are arranged in one plane and the two anodes 6 and 1 are located parallel to the plane of the flat cathodes. The entire electrodes heretofore referred to are mounted in a disc 9 of ceramic material which is sealed to the open end of the envelope 1. The lead-in conductors to the electrodes may be carried through the disc 9 or by sealing through the closed end of the envelope. In the Fig. 1 the leads to the anodes 6 and I are shown in the upper portion of the tube where a stud ID of insulation is arranged to fix the individual electrodes in their proper positions.

Reference numeral l I in the Figs. 1 and 2 indicates the location of the conductive shielding member which is provided in accordance with the main feature of this invention. Although this shielding II is shown as a coating of colloidal graphite applied on the inner wall of the envelope I, it is understood that this shielding may likewise be a cage-type of grid or any other suitable conductive means, being maintained at tained at constant potential, even the most nonuniform or non-symmetric distribution of the getter material on the inner surface of the envelope will be unable to involve any undesired or harmful effects upon the electrode systems.

What is claimed is:

1. An electron tube device for ultra short wave operation comprising, two coplanar substantially flat cathodes each having one of its major surfaces coated with an electron emissive substance in opposite directions to one another, a grid surrounding each of said cathodes, an anode on each side of said coplanar cathodes in parallel relation therewith each'anode forming one active electrode system with the oppositely positioned electron emissive surface of either cathode and its surrounding grid and also forming a neutralization system with the oppositely positioned non-emissivesurface of the other of said cathodes and its surrounding grid for neutralizing the impedances of either of said active electrode systems, conductive means encircling said active electrodes and said neutralization systems, a connection to maintain said shielding at a constant poten al, and an envelope encompassing said systems and said conductive means.

2. The invention according to claim 1, characterized in that said shielding means is a cagetype of grid.

3. An electron tube device for ultra short wave operation comprising, two coplanar substantially fiat cathodes each having one of its major surfaces coated with an electron emissive substance in opposite directions to one another, a grid surrounding each of said cathodes, an anode on either side of said coplanar cathodes in parallel relation therewith, each anode forming one active electrode system with the oppositely positioned electron emissive surface of either cathode and its surrounding grid and also forming a neutralization system with the oppositely positioned non-emissive surface of the other of said cathodes and its surrounding grid for neutralizing the impedances of either of said active electrode systems, an envelope encompassing said electrode systems, a coating of colloidal graphite applied on the inner wall of said envelope, and. a connection to maintain said coating at a constant potential.

4. An electron tube device for ultra short wave operation comprising, two coplanar substantially flat cathodes each having one of its major surfaces coated with an electron emissive substance in opposite directions to one another, a grid surrounding each of said cathodes, an anode on either side of said coplanar cathodes in parallel relation therewith, each anode forming one active electrode system with the oppositely positioned electron emissive surface of either cathode and its surrounding grid and also forming a neutralization system with the oppositely positioned non-emissive surface of the other of said cathodes and its surrounding grid for neutralizing the impedances of either of said active electrode systems, and a metallic envelope encompassing said systems and maintained at constant potential.

5. An electron tube device for ultra short wave operation, comprising two coplanar substantially fiat cathodes each having one of its major surfaces coated with an electron emissive substance in opposite directions to one another, a grid surrounding each of said cathodes, an anode on each side of said coplanar cathodes in parallel relation therewith, each anode forming one active electrode system with the oppositely positioned electron emissive surface of either cathode and its surrounding grid and also forming a neutralization system with the oppositely positioned non- .emissive surface of the other of said cathodes and its surrounding grid for neutralizing the impedances of either of said active electrode systems,

conductive means encircling said active electrodes and said neutralization systems and a connection to maintain said conductive means at a constant potential.

FELIX HERRIGER. 

